To prepare beef, combine first 6 ingredients in a zip-top plastic bag. Add 1 tablespoon red wine vinegar; seal bag. Marinate in refrigerator 2 hours.
To prepare salad, combine 1 tablespoon red wine vinegar, onion, and next 6 ingredients (onion through cucumber) in a large bowl. Cover and let stand at room temperature 2 hours, stirring occasionally.
Remove steak from bag, discarding marinade. Place the steak on grill rack coated with cooking spray; grill 5 minutes on each side or until desired degree of doneness. Let stand 5 minutes. Cut steak diagonally across grain into thin slices. Add bread and basil to cucumber mixture; toss well. Serve salad immediately with steak.